Calcium Hydroxide in Endodontics:
Calcium hydroxide has been utilized by dentists in the clinical practice for over a century1. In 1920, Herman added calcium hydroxide to dentistry as a pulp-capping material however today it’s far used broadly in the discipline of Endodontics 2 3.
calcium hydroxide is a white scentless powder with the chemical formula Ca(oh)2 and a molecular weight of 7.08. Ca(OH)2 has low dissolvability in water (around 1.2 g?L-1 at 25 oC), which decreases with increasing temperature.2 (mohammadi) The low solubility is a good clinical characteristic, since a long duration is required for Ca( OH) 2 to dissolve in tissue fluids when it is direct contact( 3) it is insoluble in alcohol, mohammadi. chemically, it is categorized as a strong base in contact with aqueous fluids (its ph is ready 12.5 – 12.8), and dissociate into calcium and hydroxyl ions 4.
Ca( OH) 2 2 in in water has a thixotropic actions, that basically means that it is very fluid when agitated.3 When Ca(OH)2 is exposed to carbon dioxide (CO2) or carbonate ions (CO3-) in biological tissue, the dissociation of the chemical leads to the formation of calcium carbonate (CaCO3) and an overall consumption of Ca2+ ions. However, one study showed that after 30 days of exposure to carbon dioxide, six preparations of Ca(OH)2 still maintained a purportedly bactericidal pH within the root canal.2Mohammadi
Calcium hydroxide is utilized and provided in different Forms. It is used like a varnish when supplied as a liquid containing calcium hydroxide suspended in a solvent or when supplied as a paste in which calcium hydroxide is suspended in methyl cellulose. some other form of calcium hydroxide is advertised as a base and a catalyst. By utilizing the catalyst, calcium hydroxide responds quicker and forms a hard, amorphous compound inside in the oral environment in minutes. At long last, calcium hydroxide provided as a paste contains a polymer resin that can be cured when exposed to a blue light source 2.
in recent times, calcium hydroxide is widely used within the field of endodontics due to its
benefits such as:
Antimicrobial Effect of Calcium Hydroxide
Microorganisms are the main cause of apical inflammatory lesions and the ultimate goal of endodontic treatment is to avoid and control pulp and periradicular infections(1 Anti microbial) . Many measures have been introduced to limit the number of microorganisms from the root canal system , Such as various techniques for mechanical instrumentation , Irrigation solutions and technique and intra -canal medicaments.(2-6)Anti-mic. It is difficult to remove all microorganisms from an infected root canal system by mechanical instruments alone.7-9. Therefore chemical irrigation and disinfection are important to remove microorganisms, Their by- products , Pulp tissue and other residues and debris from the root canal system. Intracanal medicaments can play these functions by remaining in the root canal between treatment appointments.10
Endodontic infections happen as a result of microbial mixtures containing bacteria represented by Enterococcus faecalis 6 and fungi, particularly those dominated by Candida Candida 7. Anaerobic bacteria with their endotoxins on their cell walls also dominate this microbial diversity and can be detected particularly gram- negatively 8.
3.1. Mechanism of Action The main effects of Ca( OH) 2 are attributed to the action of calcium and hydroxy ions on vital tissues, by inducing hard tissue deposition and acting antibacterially.17 Anti
Hydroxyl ions are primarily responsible for the strongly alkaline nature of Ca ( OH ) 2. Most Pathogens cannot survive in the strongly alkaline environment that is provided by Ca(OH) 2. (18) Anti
Since the pH value of Ca( OH) 2 is about 12.5, bacteria in the infected root canal are destroyed and eliminated while being in direct contact with this substance.3 ANTI
According to Siqueira, the antimicrobial activity of Ca( OH) 2 is associated with the release of hydroxy ions in contact with aqueous fluids. Siqueira and Lopes6 (Mohammadi ) proposed that hydroxyl ions are extremely highly oxidative free radicals that demonstrate intense reactivity with biomolecules.19
The fatal effect on microorganisms has been related to the following mechanisms- damage to the bacterial cytoplasmic membrane, protein denaturation and/or DNA damage- but it is difficult to determine the main mechanism for bacterial death.20- 23
Hydroxy ions from Ca( OH) 2 impose their mode of action in the cytoplasmic membrane, where enzymatic sites are located.7 MOhammmadi
Extracellular enzymes have an effect on nutrients, carbohydrates, proteins and lipids which favor digestion through hydrolysis. Intracellular enzymes in the cell promote the respiratory of the cell wall structure. The pH gradient of the cytoplasmic membrane is influenced by the high concentration of hydroxylions of calcium hydroxide, which act on the proteins of the membrane( protein denaturation). The high pH of Ca( OH) 2 affects the integrity of the cytoplasmic membrane by chemical disruption to the organic components and transport of nutrients or by destruction of phospholipids or unsaturated fatty acids of the cytoplasmic membrane during the peroxidation process. That is called saponification reaction.8 MOHAMMADI
The adjustment of intracellular intracellular pH pH is affected by multiple cellular processes such as cellular metabolism, shape changes, mobility, adaptation of transporters and polymerization of cytoskeletal components, activation of cellular proliferation and growth, conductivity and transport through the membrane and isosmotic cell volume. Therefore, many cellular functions can be influenced by pH, including enzymes essential for cellular metabolism.9 Estrela et al.10 found that bacterial enzymatic inactivation under extreme pH conditions is irreversible over a long period of time. MOHAMMMADI
Kontakiotis et al. pointed out that the capacity of Ca( OH) 2 to absorb carbon dioxide could be related to its antibacterial activity.24
Calcium hydroxide has an antibacterial effect in the root canal system as long as a high pH value is maintained.6 (MOHAMMADI) An in vivo study showed that root canals treated with Ca( OH) 2 exhibited fewer bacteria than those treated with camphorated phenol or camphorated monochlorophenol.11 (MOHAMMADI) In another study it was reported that Ca(OH)2 effectively prevents the growth of micro- organisms, but is only presented to a limited extent compared to camphorated chlorophenol, which emphasises the need for direct contact to achieve optimal antibacterial action.12 MOH It was shown that a 7-day application of a Ca( OH) 2 drug was adequate to decrease the canal bacteria to a point that resulted in a negative culture.13 MOH Study demonstrated that an aqueous Ca( OH) 2 paste and a silicone oil based Ca( OH) 2 paste are effective in eliminating Enterococcus faecalis in dentin tubules.14MOH Estrela et al.15 showed that both the direct exposure test and the agar diffusion test are useful for determining the antimicrobial range of Ca( OH) 2 and in creating enhanced infection control protocols. In both tests, a complete antimicrobial effect after 48 h was observed independently of the Ca( OH) 2 paste as vehicle.15 MOH Another study revealed that Ca( OH) 2 reduced the number of E. Faecalis in all depths within dentin tubules up to 24 hours, and that less viscous Ca( OH) 2 preparations were more potent in eliminating E. faecalis from dentinal tubules than were viscous preparations.16 MOH
In In a a study to examine the effect of electrophoretically activated Ca( OH) 2 on the viability of bacteria in dentine tubules, Lin et al.17MOH revealed that treatment with electrophoresis to depths of 200 to 500 ?m was significantly more effective than pure Ca( OH) 2. Samples treated with electrophoretically activated Ca( OH) 2 did not show viable bacteria in dentin tubules within 7 days to a depth of 500 ?m from the root canal space.17 MOH
it has been demonstrated that Faecalis cells are much more sensitive to Ca( OH) 2 in the exponential growth phase and are killed within 3 s to 10 min. Cells in a stationary phase were more resistant and living cells were obtained after 10 minutes. However, cells in a starvation phase were the most resistant and were not completely eliminated during a 10-minute test period.18 MOH
In contrast, several more studies have demonstrated the ineffectiveness of Ca( OH) 2 in removing bacterial cells. Two studies showed that Ca( OH) 2 had no antibacterial effect as a paste or as a commercial intracanal medicament if used against Streptococcus sanguis. 19,20 MOH It has also been shown that a Ca( OH) 2 paste (Calasept; Speiko, Darmstadt, Germany) does not eliminate E.faecalis even superficially in dentin tubules.21MOH Safavi et al.22 pointed out that E. Faecium remained viable after relatively longer treatment times with Ca( OH) 2 / saline solution in dentine tubules. Another study showed that Ca( OH) 2 can take up to 10 days to clean dentin tubules infected with facultative bacteria.23MOH Siqueira and Uzeda24 showed that Ca( OH) 2, mixed with saline, was ineffective in removal of E. faecalis and E. faecium inside dentinal tubules after one contact week.Estrela et al.8 MOH observed that Ca( OH) 2 in infected dentin tubules had no antimicrobial effect on Sfaecalis, Saureus, Bacillus subtilis, Pseudomonas aeruginosa or the bacterial mixture used during the entire experiment. It has been shown that the viability of E. Faecalis in infected root dentine was not affected by Ca( OH) 2.25 MOH In a systematic review to evaluate the antibacterial efficacy of Ca( OH) 2, Sathorn et al.26 indicates that Ca( OH) 2 had restricted efficacy in removing bacteria from the human root canal when examined by culture techniques.
In a polymerase chain reaction( PCR) study to assess the impact of root canal filling with or without prior Ca( OH) 2 or 2% chlorhexidine( CHX) on the persistence of bacterial DNA in infected dentin tubules. Cook et al.27 MOH demonstrated that a 2% CHX treatment followed by canal filling was more effective in eliminating the DNA of E. faecalis than application of Ca( OH) 2 or immediate canal filling. In failed root canal treatments, a 2% CHX gel was a more efficient than Ca(OH)2 paste against E. faecalis when used as intra canal medicament.28 MOH Krithikadatta et al.29 pointed out that 2% CHX gel alone is more effective than ca( oh) 2 against E. faecalis. Another study showed that a polymeric chlorhexidine- controlled release device was significantly more effective in decreasing intradentinal bacteria than Ca( OH) 2( Table 1) .30 MOH
Peters et al. noted that the number of positive gram bacteria in the root canal system increased after dressing with calcium hydroxide 13. Rev 2016